The present invention relates to an ultrasonic diagnostic apparatus for clearly plotting an image of a blood vessel wall, for example, and a method of processing an ultrasound signal.
Heretofore, intravascular ultrasonic diagnostic apparatus have widely been used for the diagnosis of arteriosclerosis, the preoperative diagnosis for an intravascular treatment such as percutaneous transluminal coronary angioplasty, and the postoperative observation of an intravascular treatment. The intravascular ultrasonic diagnostic apparatus detect a reflected echo of an ultrasonic wave emitted from an ultrasonic transducer disposed in a catheter tube and convert the detected echo into an image. When an image of a blood vessel wall is generated from the ultrasonic echo, it is affected by an ultrasonic echo reflected from blood cells that are flowing through the blood vessel. The ultrasonic echo reflected from blood cells tends to blur the boundary between the blood vessel wall and the blood vessel lumen in the resultant image, adversely affecting the diagnostic accuracy. Though it is generally understood that the diagnostic accuracy is increased at higher frequencies of ultrasound signals, there is a certain limitation on the diagnostic accuracy because the reflected echo from blood cells increases at higher ultrasound signal frequencies.